diff mbox series

[v7,3/3] KVM: vmx: handle vm-exit for UMWAIT and TPAUSE

Message ID 20190712082907.29137-4-tao3.xu@intel.com (mailing list archive)
State New, archived
Headers show
Series KVM: x86: Enable user wait instructions | expand

Commit Message

Tao Xu July 12, 2019, 8:29 a.m. UTC 
As the latest Intel 64 and IA-32 Architectures Software Developer's
Manual, UMWAIT and TPAUSE instructions cause a VM exit if the
RDTSC exiting and enable user wait and pause VM-execution
controls are both 1.

This patch is to handle the vm-exit for UMWAIT and TPAUSE as this
should never happen.

Co-developed-by: Jingqi Liu <jingqi.liu@intel.com>
Signed-off-by: Jingqi Liu <jingqi.liu@intel.com>
Signed-off-by: Tao Xu <tao3.xu@intel.com>
---

Changes in v7:
    - Add nested exit reason for UMWAIT and TPAUSE (Paolo)
---
 arch/x86/include/uapi/asm/vmx.h |  6 +++++-
 arch/x86/kvm/vmx/nested.c       |  3 +++
 arch/x86/kvm/vmx/vmx.c          | 16 ++++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

Comments

Sean Christopherson July 12, 2019, 4:03 p.m. UTC | #1 
On Fri, Jul 12, 2019 at 04:29:07PM +0800, Tao Xu wrote:
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5213,6 +5213,9 @@ bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
>  	case EXIT_REASON_ENCLS:
>  		/* SGX is never exposed to L1 */
>  		return false;
> +	case EXIT_REASON_UMWAIT: case EXIT_REASON_TPAUSE:

Grouped case statements are usually stacked vertically, e.g.:

	case EXIT_REASON_UMWAIT:
	case EXIT_REASON_TPAUSE:

> +		return nested_cpu_has2(vmcs12,
> +			SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE);
>  	default:
>  		return true;
>  	}
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 0787f140d155..e026b1313dc3 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5349,6 +5349,20 @@ static int handle_monitor(struct kvm_vcpu *vcpu)
>  	return handle_nop(vcpu);
>  }
>  
> +static int handle_umwait(struct kvm_vcpu *vcpu)
> +{
> +	kvm_skip_emulated_instruction(vcpu);
> +	WARN(1, "this should never happen\n");

Blech.  I'm guessing this code was copy-pasted from handle_xsaves() and
handle_xrstors().  The blurb of "this should never happen" isn't very
helpful, e.g. the WARN itself makes it pretty obvious that we don't expect
to reach this point.  WARN_ONCE would also be preferable, no need to spam
the log in the event things go completely haywire.

Rather than propagate ugly code, what about defining a common helper, e.g.

static int handle_unexpected_vmexit(struct kvm_vcpu *vcpu)
{
	kvm_skip_emulated_instruction(vcpu);
	WARN_ONCE(1, "Unexpected VM-Exit = 0x%x", vmcs_read32(VM_EXIT_REASON));
	return 1;
}

...
{
	[EXIT_REASON_XSAVES]                  = handle_unexpected_vmexit,
	[EXIT_REASON_XRSTORS]                 = handle_unexpected_vmexit,

	[EXIT_REASON_UMWAIT]                  = handle_unexpected_vmexit,
	[EXIT_REASON_TPAUSE]                  = handle_unexpected_vmexit,

}

> +	return 1;
> +}
> +
> +static int handle_tpause(struct kvm_vcpu *vcpu)
> +{
> +	kvm_skip_emulated_instruction(vcpu);
> +	WARN(1, "this should never happen\n");
> +	return 1;
> +}
> +
>  static int handle_invpcid(struct kvm_vcpu *vcpu)
>  {
>  	u32 vmx_instruction_info;
> @@ -5559,6 +5573,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
>  	[EXIT_REASON_VMFUNC]		      = handle_vmx_instruction,
>  	[EXIT_REASON_PREEMPTION_TIMER]	      = handle_preemption_timer,
>  	[EXIT_REASON_ENCLS]		      = handle_encls,
> +	[EXIT_REASON_UMWAIT]                  = handle_umwait,
> +	[EXIT_REASON_TPAUSE]                  = handle_tpause,
>  };
>  
>  static const int kvm_vmx_max_exit_handlers =
> -- 
> 2.20.1
>
Tao Xu July 13, 2019, 2:22 p.m. UTC | #2 
On 7/13/2019 12:03 AM, Sean Christopherson wrote:
> On Fri, Jul 12, 2019 at 04:29:07PM +0800, Tao Xu wrote:
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -5213,6 +5213,9 @@ bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
>>   	case EXIT_REASON_ENCLS:
>>   		/* SGX is never exposed to L1 */
>>   		return false;
>> +	case EXIT_REASON_UMWAIT: case EXIT_REASON_TPAUSE:
> 
> Grouped case statements are usually stacked vertically, e.g.:
> 
> 	case EXIT_REASON_UMWAIT:
> 	case EXIT_REASON_TPAUSE:
>Ok, thank you for your suggestion.

>> +		return nested_cpu_has2(vmcs12,
>> +			SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE);
>>   	default:
>>   		return true;
>>   	}
>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>> index 0787f140d155..e026b1313dc3 100644
>> --- a/arch/x86/kvm/vmx/vmx.c
>> +++ b/arch/x86/kvm/vmx/vmx.c
>> @@ -5349,6 +5349,20 @@ static int handle_monitor(struct kvm_vcpu *vcpu)
>>   	return handle_nop(vcpu);
>>   }
>>   
>> +static int handle_umwait(struct kvm_vcpu *vcpu)
>> +{
>> +	kvm_skip_emulated_instruction(vcpu);
>> +	WARN(1, "this should never happen\n");
> 
> Blech.  I'm guessing this code was copy-pasted from handle_xsaves() and
> handle_xrstors().  The blurb of "this should never happen" isn't very
> helpful, e.g. the WARN itself makes it pretty obvious that we don't expect
> to reach this point.  WARN_ONCE would also be preferable, no need to spam
> the log in the event things go completely haywire.
> 
> Rather than propagate ugly code, what about defining a common helper, e.g.
> 
> static int handle_unexpected_vmexit(struct kvm_vcpu *vcpu)
> {
> 	kvm_skip_emulated_instruction(vcpu);
> 	WARN_ONCE(1, "Unexpected VM-Exit = 0x%x", vmcs_read32(VM_EXIT_REASON));
> 	return 1;
> }
> 
> ...
> {
> 	[EXIT_REASON_XSAVES]                  = handle_unexpected_vmexit,
> 	[EXIT_REASON_XRSTORS]                 = handle_unexpected_vmexit,
> 
> 	[EXIT_REASON_UMWAIT]                  = handle_unexpected_vmexit,
> 	[EXIT_REASON_TPAUSE]                  = handle_unexpected_vmexit,
> 
> }
> 
Thank you Sean, I will do this in next version of patch.

>> +	return 1;
>> +}
>> +
>> +static int handle_tpause(struct kvm_vcpu *vcpu)
>> +{
>> +	kvm_skip_emulated_instruction(vcpu);
>> +	WARN(1, "this should never happen\n");
>> +	return 1;
>> +}
>> +
>>   static int handle_invpcid(struct kvm_vcpu *vcpu)
>>   {
>>   	u32 vmx_instruction_info;
>> @@ -5559,6 +5573,8 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
>>   	[EXIT_REASON_VMFUNC]		      = handle_vmx_instruction,
>>   	[EXIT_REASON_PREEMPTION_TIMER]	      = handle_preemption_timer,
>>   	[EXIT_REASON_ENCLS]		      = handle_encls,
>> +	[EXIT_REASON_UMWAIT]                  = handle_umwait,
>> +	[EXIT_REASON_TPAUSE]                  = handle_tpause,
>>   };
>>   
>>   static const int kvm_vmx_max_exit_handlers =
>> -- 
>> 2.20.1
>>
diff mbox series

Patch

diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
index d213ec5c3766..d88d7a68849b 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -85,6 +85,8 @@ 
 #define EXIT_REASON_PML_FULL            62
 #define EXIT_REASON_XSAVES              63
 #define EXIT_REASON_XRSTORS             64
+#define EXIT_REASON_UMWAIT              67
+#define EXIT_REASON_TPAUSE              68
 
 #define VMX_EXIT_REASONS \
 	{ EXIT_REASON_EXCEPTION_NMI,         "EXCEPTION_NMI" }, \
@@ -142,7 +144,9 @@ 
 	{ EXIT_REASON_RDSEED,                "RDSEED" }, \
 	{ EXIT_REASON_PML_FULL,              "PML_FULL" }, \
 	{ EXIT_REASON_XSAVES,                "XSAVES" }, \
-	{ EXIT_REASON_XRSTORS,               "XRSTORS" }
+	{ EXIT_REASON_XRSTORS,               "XRSTORS" }, \
+	{ EXIT_REASON_UMWAIT,                "UMWAIT" }, \
+	{ EXIT_REASON_TPAUSE,                "TPAUSE" }
 
 #define VMX_ABORT_SAVE_GUEST_MSR_FAIL        1
 #define VMX_ABORT_LOAD_HOST_PDPTE_FAIL       2
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index a4d5da34b306..9f91f834ec43 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5213,6 +5213,9 @@  bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
 	case EXIT_REASON_ENCLS:
 		/* SGX is never exposed to L1 */
 		return false;
+	case EXIT_REASON_UMWAIT: case EXIT_REASON_TPAUSE:
+		return nested_cpu_has2(vmcs12,
+			SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE);
 	default:
 		return true;
 	}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0787f140d155..e026b1313dc3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5349,6 +5349,20 @@  static int handle_monitor(struct kvm_vcpu *vcpu)
 	return handle_nop(vcpu);
 }
 
+static int handle_umwait(struct kvm_vcpu *vcpu)
+{
+	kvm_skip_emulated_instruction(vcpu);
+	WARN(1, "this should never happen\n");
+	return 1;
+}
+
+static int handle_tpause(struct kvm_vcpu *vcpu)
+{
+	kvm_skip_emulated_instruction(vcpu);
+	WARN(1, "this should never happen\n");
+	return 1;
+}
+
 static int handle_invpcid(struct kvm_vcpu *vcpu)
 {
 	u32 vmx_instruction_info;
@@ -5559,6 +5573,8 @@  static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
 	[EXIT_REASON_VMFUNC]		      = handle_vmx_instruction,
 	[EXIT_REASON_PREEMPTION_TIMER]	      = handle_preemption_timer,
 	[EXIT_REASON_ENCLS]		      = handle_encls,
+	[EXIT_REASON_UMWAIT]                  = handle_umwait,
+	[EXIT_REASON_TPAUSE]                  = handle_tpause,
 };
 
 static const int kvm_vmx_max_exit_handlers =